hineas
03-28-2022, 08:58 AM
Even though we have already solved the issue, I am sharing this since it might help others with similar problems.
We have the BluePrint 347 with the Holley Sniper EFI in the Mk4. The issues started at about 400 miles on the odometer.
Over the past week or so our Mk4 has had a long crank time. This kept getting worse and then it started to run rough for about 10 seconds after starting and would spit out black exhaust. During that 10 seconds the engine felt like it was going to die and it was hard to get the RPMs above 500. After the first 10 seconds the car smoothed out and ran fine except for wanting to idle at about 1100-1400 rpms. There were no power issues and everything seemed to be working fine. Engine temps were spot on, about 180-185F. Good oil pressure. Full tank of gas. Etc.
A few days ago I pulled into a gas station. I started the vehicle and it just happened that the vehicle was idling for a few minutes. When I backed up there was a pool of coolant under the car. I popped the hood and coolant was coming out of the expansion tank. I looked at the dash temp and it was about 240F. I shut the engine off. I was surprised since the temp is always 180-190F. I watch the coolant temp closely and it always runs cool. I also had seen the temp when I pulled into the gas station and it was normal. This happened when idling at a complete stop.
I turned the key on to look at the hand controller for the EFI. Typically if the temp is at 190F when I shut it off the EFI turns the electric fan on when the key is turned on. I noticed that the fan wasn't on. I checked the engine temp on the EFI and it just said that the coolant temp was low and that the sensor had failed. Then the temp jumped to 302F on the hand controller (but the dash was still saying about 210F).
We reprogrammed the fan on the EFI to turn on at -30F so it would just stay on. We let the engine cool and then the car had a rough start and then ran fine. I was able to drive the car home.
I replaced the coolant temp sending unit and the car is back to normal. The rough starts are a thing of the past. It no longer has a long crank. It is great.
The car was running rich because the the EFI thought the engine was really cold. That is why there was soot in the exhaust and it wasn't running well. I ended up pulling the oxygen sensor and there was a super thin amount of soot but still looked good. I pulled the spark plugs and there was soot at the threads but the sparking element was clean. I think we found the issue soon enough that we didn't foul the plugs or the sensor. All is good now, the car starts with only about 1 second of cranking, it idles better, and it is smooth.
We have the BluePrint 347 with the Holley Sniper EFI in the Mk4. The issues started at about 400 miles on the odometer.
Over the past week or so our Mk4 has had a long crank time. This kept getting worse and then it started to run rough for about 10 seconds after starting and would spit out black exhaust. During that 10 seconds the engine felt like it was going to die and it was hard to get the RPMs above 500. After the first 10 seconds the car smoothed out and ran fine except for wanting to idle at about 1100-1400 rpms. There were no power issues and everything seemed to be working fine. Engine temps were spot on, about 180-185F. Good oil pressure. Full tank of gas. Etc.
A few days ago I pulled into a gas station. I started the vehicle and it just happened that the vehicle was idling for a few minutes. When I backed up there was a pool of coolant under the car. I popped the hood and coolant was coming out of the expansion tank. I looked at the dash temp and it was about 240F. I shut the engine off. I was surprised since the temp is always 180-190F. I watch the coolant temp closely and it always runs cool. I also had seen the temp when I pulled into the gas station and it was normal. This happened when idling at a complete stop.
I turned the key on to look at the hand controller for the EFI. Typically if the temp is at 190F when I shut it off the EFI turns the electric fan on when the key is turned on. I noticed that the fan wasn't on. I checked the engine temp on the EFI and it just said that the coolant temp was low and that the sensor had failed. Then the temp jumped to 302F on the hand controller (but the dash was still saying about 210F).
We reprogrammed the fan on the EFI to turn on at -30F so it would just stay on. We let the engine cool and then the car had a rough start and then ran fine. I was able to drive the car home.
I replaced the coolant temp sending unit and the car is back to normal. The rough starts are a thing of the past. It no longer has a long crank. It is great.
The car was running rich because the the EFI thought the engine was really cold. That is why there was soot in the exhaust and it wasn't running well. I ended up pulling the oxygen sensor and there was a super thin amount of soot but still looked good. I pulled the spark plugs and there was soot at the threads but the sparking element was clean. I think we found the issue soon enough that we didn't foul the plugs or the sensor. All is good now, the car starts with only about 1 second of cranking, it idles better, and it is smooth.